1. Field of the Invention
The present invention relates to an information processing apparatus, such as a personal computer having a cooling fan. In particular, the present invention relates to an information processing apparatus, which enables fan control of achieving both cooling performance traceability with rise in temperature, and reduction of non-continuous sound.
2. Description of the Related Art
In many cases, an information processing apparatus such as a personal computer is equipped with a cooling fan for releasing heat of a housing outside and blowing air toward exothermic objects. In general, this kind of information processing apparatus controls a cooling fan rate stepwise.
Conventionally, stepwise rate control of the cooling fan has been carried out in the same manner in both cases where temperature rises and falls. For example, three-stage control means that both acceleration and deceleration of the cooling fan are controlled in three stages. For this reason, the following situation is given depending on load; more specifically, acceleration and deceleration are readily repeated. As a result, a non-continuous sound, such as an annoying noise is frequently made.
In view of such circumstances, the following method has been proposed in order to reduce the non-continuous sound (e.g., see JPN. PAT. APPLN. KOKAI Publication No. 11-272365,). According to the method, if the cooling fan is operated at a low rate with a fall of temperature, deceleration is made only when a predetermined time or more elapses after a rate change is finally made.
However, the cooling performance traceability in a rise of temperature required for the cooling fan must be preferentially taken into consideration. If multi-stage control is carried out, the rate difference caused between stages inevitably takes a large value to some degree. In other words, even if the method disclosed in the foregoing Publication No. 11-272365 is employed, the following problem arises. More specifically, when the cooling fan is decelerated, the rate difference becomes large (sudden change) before and after deceleration. For this reason, the reduction of non-continuous noise is not achieved even if deceleration is made while maintaining regular intervals or more.